In the technology of model submarines, the prior art has resorted to two different design philosophies, namely: a positive buoyancy system (or "PBS") and a negative buoyancy system (or "NBS"), respectively. Unfortunately, there are serious disadvantages inherent in both designs.
In the PBS system, the model submarine is "trimmed" to be slightly positively buoyant when the ballast tank (or tanks) are fully flooded. If propulsion is lost, the boat will slowly rise to the surface so that at least its periscope is above the surface of the water. Thus, a model submarine employing the positive buoyancy system is "fail safe"; that is, the boat cannot sink to the bottom in the event of a power failure but, rather, may be retrieved by the operator.
However, when submerged, model submarines employing PBS have great difficulty in simulating the maneuvers of its full-size counterpart. This is due, at least in part, to the dynamic forces acting on the bow and stern planes which are used to submerge the boat under the surface of the water. Control of the angle of attack of these planes (in order to maintain a level run at a given depth) is most difficult to achieve, especially if the boat cannot be seen by the operator. Thus, the enjoyment and satisfaction in operating a PBS boat have been one greatly curtailed and sacrificed inn favor of a fail-safe retrieval.
In the NBS system, on the other hand, the model submarine is "trimmed" to be slightly negatively buoyant when the ballast tank (or tanks) are fully flooded. While the intention of the NBS system is to enable the model submarine to more closely simulate the maneuvers of its full-size counterpart, nevertheless, it is difficult to control the model submarine and maintain a level run at a given depth (for the same reasons as the PBS system). Moreover, should propulsion cease or a failure occur, the boat can sink to the bottom of a lake (or other body of water) in which case retrieval can be quite inconvenient or altogether impossible. If the boat cannot be retrieved, a substantial investment (amounting to hundreds of dollars) is lost.
Model enthusiasts have long sought a submarine which can accurately and realistically simulate the maneuvers of its real life counterpart, yet has an inherent fail-safe characteristic, as well as an automatic depth control system which levels the boat upon reaching the command depth.
Neither the PBS or the NBS systems currently employed in model submarines are satisfactory; and because of their inherent disadvantages (primarily, the lack of an automatic depth control feature) the use and enjoyment of model submarines have been greatly curtailed, such that the market for model submarines has been restricted and does not even begin to approach the comparable market for other models, such as model cars, boats and airplanes.
Moreover, the existing model submarines (or kits thereof) tend to be unduly complicated, costly and unreliable; and as a result, the market for model submarines has been restricted even further.
For example, various techniques have been employed to satisfactorily attempt to fill and purge the ballast during diving operations. Many models employ reversible pumps which pump water into or out of one or more ballast tanks. Other models use free flooding of the ballast tank (or tanks) by opening a vent valve which communicates with the top of the tank, thereby allowing water to enter through a grate at the bottom of the tank, and thereby taking on a sufficient quantity of water to submerge the submarine. In order to surface, these models close the vent valve and then purge the water out of the bottom grate of the tank using compressed air, Freon or the like. To aid in trimming, these models usually resort to at least two ballast tanks, one fore and one aft; and each ballast tank is provided with its own respective flooding and purging means. Alternatively, to aid in trimming, some models utilize a weight carried by a servo-controlled travelling lead screw which shifts the weight, thereby altering the model's center of gravity. In such methods, the weight is usually positioned in a ballast tank. These design arrangements (heretofore resorted to in the prior art) are complicated, costly and unreliable.
Additionally, most of the submarine kits presently on the market also require various separate watertight compartments in order to house the electric motors, electronics, servo-motors and (often) the batteries. Watertight shaft seals are therefore required at bulkhead penetrations for propeller shafts, servo-actuator linkages and controls, wire penetrators and the like. These bulkhead penetrations are all potential leakage sites which could lead to short circuiting, flooding and power loss, thereby possibly resulting in the loss of the model submarine. Thus, these penetrations require precise sealing arrangements to effect the required leak-tight integrity, thereby adding unnecessary cost and ultimately detracting from reliability of the product.
In my previous U.S. Pat. No. 2,914,887 issued on Dec. 1, 1959 and entitled "Toy Submarine", a battery-operated electric motor drives a conventional propeller for forward movement of the submarine. A ballast tank (below the sail) has a valve for admitting water into the ballast tank. The valve is connected to a float connected to a lever. When the float lever is flipped upwardly, the boat rides on the surface of the water; and when the float lever is pushed down, water enters into the ballast tank, and the boat submerges to its periscope depth. The float lever may be held down by a latch, if desired, but the boat cannot dive below its periscope depth. While satisfactory for the purposes intended, nevertheless, it will be appreciated that the model disclosed in my earlier '887 patent (vintage 1959) does not have the sophisticated technology, nor the improved features and advantages contributing to the marketability of the present invention.
Further representative of the prior art are the following patent references:
______________________________________ Inventor(s) U.S. Pat. No. ______________________________________ Hueber et al 2,022,642 Lord 2,044,088 Gordon 3,010,255 Presnell 3,036,403 Parken et al 3,165,390 Gibson 3,181,272 Chalom 3,545,886 Germany 2,525,253 Germany 3,244,565 France 830,268. ______________________________________
None of these patent references, nor any other prior publications or commercial uses known to the applicant herein, are completely satisfactory for the purposes intended; but rather, have inherent disadvantages and deficiencies which seriously curtail the use and enjoyment of model submarines and, ultimately, their market acceptance.